Vesicular membranes are intimately involved in the storage, transport and release of regulatory and metabolic agents in cellular systems. To function properly these vesicles must be able to actively accumulate these agents, retain them for periods of time and then expel them to an external environment by fusion with a limiting membrane. It is our objective to understand at a molecular level factors which affect these stability, fusion and solute concentration properties and to use that understanding in the design of useful artificial analogues. These objectives will be pursued largely through the study of model Thospholipid vesicles. The thermodynamics of vesicle fusion as stimulated by divalent cations in mixed anionic lipid systems will be studied calorimetrically and correlation with structural changes will be established through the use of nuclear magnetic resonance spectroscopu. The nature of the fusion stimulating complex will be studied by a variety of nuclear magnetic resonance techaniques including 1H, 19F, 13C and 31P nmr. Chemical models for active concentration of solutes in vesicles will also be studied using magnetic resonance. Methods of concentrating catecholamines and drugs used in liposome chemotherapy will be developed and studied.